In an existing Long Time Evolution (LTE) system, generally a User Equipment (UE) communicates with only one Access Point (AP) in an uplink direction (that is, the UE sends a signal to the AP) and in a downlink direction (that is, the AP sends signals to the UE), where the AP is called a serving AP, and an uplink serving AP and a downlink serving AP is the same AP. The AP is a node including at least a radio frequency transceiver and may be equipped with one or multiple antenna elements; multiple APs may be distributed or centralized geographically and connected to an eNodeB over a wired or wireless connection; or the AP and eNodeB may be the same physical entity. The relationship between an AP and a cell may be as follows. A cell includes one AP, or a cell includes multiple APs. For ease of description, the following assumes that a cell includes one AP.
In such a system, the uplink transmitting power of the UE may be based on downlink signaling of the base station eNodeB and/or the measurement result of a radio channel measured by the UE. For example, the transmitting power of a Physical Uplink Share Channel (PUSCH) of the UE is decided by multiple factors, which include downlink Path Loss (abbreviated to PL) measured by the UE, cell-specific power adjustment PO—NORMINAL—PUSCH(j) sent by the AP to the UE, and UE-specific power adjustment PO—UE—PUSCH(j) sent by the AP to the UE. Therefore, the UE receives the downlink signaling sent by the serving AP to obtain PO—NORMINAL—PUSCH(j) and PO—UE—PUSCH(j), measures the downlink signal sent by the serving AP to obtain the PL, and calculate the uplink transmitting power value considering other parameters.
In the process of implementing the present invention, the inventor finds that in the communication system, the introduction of multiple technologies, such as Coordinated Multi-Point transmission (CoMP), different uplink and downlink serving cells, and relay transmission, brings forth a new scenario. For example, the CoMP technology is an important way to improve the overall performance of a cell and the performance of the cell serving a UE at the cell edge, and multiple APs may coordinate in transmitting and receiving data from the UE (the APs may be connected to the same eNodeB or to different base stations) and therefore a new scenario may be introduced, that is, the uplink and downlink serving APs may be the same or different. If the existing uplink power control algorithm is applied directly, a certain problem may occur during uplink power control. Specifically, among parameters of the uplink power control formula, the cell-specific parameters (such as the PO—NORMINAL—PUSCH(j) value) and UE-specific parameters (such as the PO—UE—PUSCH(j) value) are obtained by the UE from an AP that sends downlink signaling; if the AP is different from the uplink serving AP of the UE, the uplink signal power obtained according to the parameters does not match the power expected by the uplink serving AP. In addition, among the parameters of the uplink power control formula, the PL is obtained by the UE by measuring downlink signals of an AP. If the AP is different from the uplink serving AP of the UE, the uplink signal power obtained according to the PL parameter does not match the power expected by the uplink serving AP.